On the Knights of Noromath server, we have created support for several undead templates that can be acquired through the course of play. Some information about the specific spells which have been changed to provide this support is included in our Spell Changes post (this site).
Note: All undead risk destruction by treading upon holy ground. Holy grounds include most places of worship and some more prominent shrines. These places are considered to be vested with such divine essence that no cleric is required to be present for the grounds to present a risk to undead. In ancient ruins, the boundaries of holy grounds may not be obvious at all, presenting very real perils for undead wishing to pass by.
These creatures have long existed in the Realms and sages often debate their true nature and purpose. Some claim they are powered by the raw essence of vengeance itself. What can be agreed upon is that they are undead creatures with few weaknesses. The terms by which they are created are poorly understood, and there are those who think that a Revenant could be given unlife beyond its vengeance pact with access to the right magic.
These are the still-living victims of vampires, who have acquired some degree of vampiric affliction themselves. This alarming condition may be unique to certain strains of vampirism existing in the south. It may be difficult or impossible to detect. When a vampire thrall would normally die from their wounds or some other cause, they instead become a vampire, sometimes with disastrous results. A vampire thrall that is killed in daylight, for example, would immediately be subjected to the effects of daylight as a vampire.
These creatures are well known in the Realms for their wickedness and yet there are still lineages of them which have endured for thousands of years. Finding ways to exist alongside their prey, vampires are perhaps among the most insidious foes among the undead. All vampires possess common traits such as damage reduction against all but silver weaponry, and they are known to have the command of several forms of nocturnal animals and that of a vaguely humanoid mist. Vampires can also magically compel mortals to do their bidding, and they must drink the blood of sentient creatures in order to continue their damned existence. Vampires in particular are known to be vulnerable to mirrors, sunlight, and holy water. Known methods of creation include curses, magical disease, and being bitten by another vampire.
This terrible state of being is rumored to actually be the soul of a vampire, separated from its physical body, usually by way of sunlight. It is the most vile state of existence and worse than any death in any hell. Crimson Deaths are forced to languish in swamps where they suck the blood from the unfortunate creatures they prey upon, perhaps forever. Cursed beyond reckoning, these creatures are not unintelligent nor are they above making arrangements which are advantageous to them. They must feed on sentient creatures in order to persist, and they have very few weaknesses. Some claim that through dark pacts or powerful magic such as the will of a god, Crimson Deaths might somehow regain their corporeal forms.
Considering themselves without flaw and above all other beings, Liches are undead creatures of pure magical essence that usually come from the ranks of powerful wizards. The process of achieving lichdom is as much legend as science, with many spellcasters attaining only parts of the secret formula to render themselves effectively immortal.